• A 9-year-old girl had a widespread papular eruption that was histologically characterized by benign histiocytes that were acid phosphatase-positive, but that lacked Langerhans' granules ultrastructurally. New lesions had continued to develop since the patient was 3 months old, and individual lesions had resolved over a period of two to three months. The histopathologic, histochemical, and ultrastructural findings in this patient were similar to those previously described for eruptive histiocytomas in adults. Papular histiocytomas in childhood may be found in histiocytosis X, reticulohistiocytoma, xanthogranuloma, xanthoma disseminatum, or eruptive histiocytoma. These diseases may be differentiated on the basis of differing histiocytic populations and the clinical courses of the lesions in each disorder.